Contour Enthusiasts Group Archives Forums General Troubleshooting P0155 light on - AFTER O2 sensor swapped out

If this light comes back on after having a new sensor installed, what is the likely cause?

1. Bad install or wrong sensor swapped out
2. Charged for work not done
3. computer problem
4. Other....

thoughts?

P0155 Upstream Heated Oxygen Sensor circuit fault - Bank No. 2.

Check to make sure it is connected properly first off.

Diagnostic Trouble Codes (DTCs) P0135 P0141, P0155 and P0161 indicate a short to ground, open, or short to VPWR in the HO2S heater circuit.

DTC/HO2S Reference List:

DTC P0135 = HO2S HTR-11

DTC P0141 = HO2S HTR-12

DTC P0155 = HO2S HTR-21

DTC P0161 = HO2S HTR-22

Possible causes:

-- Shorts to VPWR in harness or HO2S.

-- Water in connectors.

-- Cut or pulled wires.

-- Disconnected wiring.

-- Open VPWR circuit.

-- Open GND circuit.

-- Low battery voltage.

-- Corrosion or poor mating terminals.

-- Damaged HO2S heater.

-- Damaged PCM.

I just got my car back again and got my oil light problem sorted out. Sadly, after ~100 miles the CEL came back on (computer had been reset)

According to my mechanic (who is pretty knowledgable) he had run through the troubleshooting procedure and warned me that my PCM is the likely problem and that it is a "dealer only" repair.

My gas milage is fine, so it is not an urgent fix, but who buys a car with the CEL on? and does "dealer only" mean I am screwed?

here's good one, but you need to check.

Like HITMANinMI said
Make sure they connected the O2 to the wire harness.
It's happened before that someone had a part changed but they didn't connect it.

Here is a recap as my various posts and threads on this are begining to blur...

A year ago, my CEL came on with a bad O2 sensor code. The sensor was changed and the code returned. I never did anything about it as I am either too busy or too lazy to deal with it (depending on the week).

Recently, my oil light started coming on intermittently once the engine warmed up. This is far more worrisome than an o2sensor code (especially if your mpg is still fine). I took the car to the Dealer near my office. His wanted to change my oil sensor and do a whole bunch of other stuff that was unnecesary for $1300.

I dropped my car off at pep boys and had them do the 60,000 mile tune-up and swap the o2 sensor (I forgot it was changed before) and replace the oil pressure sender. The CEL and Oil light were back on shortly after I drove off the lot.

I then took my car to a local mechanic who is a former stock car racer and master mechanic who has custom built a twin turbo 302 capable of pushing his Pantera to 230mph. He pulled out the oil sender and showed me that it was never changed (Pep Boys is going to get their ass kicked!) That problem is now fixed. He was unable to solve the CEL problem. His diagnosis was that the only likely cause left was a bad PCM.

OK, I want to deal with my CEL again. If I KNOW that the O2 sensor that is throwing the code is good, then what can I do to troubleshoot and get rid of the damn CEL?

If you have the EVTM and PCED, you can easily troubleshoot the fault with a meter and some time. The PCED gives the step-by-step procedure for isolating the fault in the O2 heater circuit.

Review the possible causes listed in my previous post. You have either a defective sensor (just because it's new doesn't mean it's good), a wiring fault, or a PCM fault.

Focus your attention on the upstream sensor closest to the radiator. If you want to verify whether or not the sensor is the fault, swap it with the other bank sensor. Note: this is a PITA.

Steve